Uplink power control (PC) is an important consideration in modern day cellular communication systems that rely on code division multiple access (CDMA) schemes, Orthogonal Frequency-Division Multiple Access (OFDMA) schemes, single carrier frequency division multiple access (SC-FDMA) schemes, etc. to manage uplink communications. Uplink PC may, for instance, control uplink transmissions in the Physical Uplink Shared Channel (PUSCH) of a long term evolution (LTE) wireless network. Specifically, uplink transmissions may undergo varying degrees of signal attenuation (e.g., path loss, etc.) as they travel through the PUSCH, and consequently may have a decreased power level upon reception. The power level of the uplink signals at reception may directly affect throughput such that uplink signals with higher power levels at reception are able to carry data at a higher bit rate. Hence, one way to increase the throughput of an individual uplink signal may be to transmit the uplink signal at a higher power level. However, increasing the transmission power of one uplink signal may also increase the degree to which that uplink signal interferes with other uplink signals in the PUSCH, thereby reducing the data throughput of those uplink signals accordingly. One way to address this problem is to develop an uplink PC solution that governs the PC settings for each of the user equipments (UEs) in a coverage region. Effective uplink PC solutions should improve network throughput while providing adequate coverage at the cell-edge.
An uplink PC solution may comprise a set of PC settings that control user equipment (UE) uplink transmissions to prevent substantial interference in the uplink channel. An optimal uplink PC solution may reduce network interference while achieving satisfactory data-throughput for all UEs in a base station's (BS's) coverage area, thereby maximizing throughput while maintaining desired network coverage. Uplink PC solutions may be computed locally at the BS level (referred to herein as the “gradient search approach”) or globally at the network level (referred to herein as the “exhaustive search approach”). The uplink PC solutions may be based on various PC computation schemes, including fractional power control, interference based power control, cell interference based power control, etc. While much of the discussion herein is in the context of a fractional power control scheme, the concepts are equally applicable to other power control schemes.
In wireless systems that manage uplink PC via the gradient search approach, each BS may unilaterally compute its own uplink PC solution based on its own measured PC parameters (i.e., irrespective of the PC solutions of other BSs). While the gradient search approach may efficiently compute locally optimal PC solutions, it may fail to achieve a globally optimal set of local PC solutions for the wireless network because it may fail to account for the effect each local PC solution will have on neighboring BSs. Specifically, changing a PC setting for a UE in one coverage area may affect the interference realization of a neighboring base station.
In wireless systems that manage uplink PC via the exhaustive search approach, a centralized PC controller may compute a globally optimized set of uplink PC solutions based on an exhaustive search of all possible uplink PC solutions for a cluster of proximately located base stations. Specifically, the globally optimized set of uplink PC solutions may be computed based at least in part on PC parameters reported by the cluster of BSs. While the exhaustive search approach may effectively compute a globally optimized set of PC solutions, the complex nature of the computation may consume large amounts of network resources (e.g., processing capacity, time, etc.). As such, a less computationally complex approach for finding a globally optimal set of uplink PC solutions is desired.